<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .content{
            height: 1000px;
            background-color: aqua;
        }

        #inner{
            position: absolute;
            top: 0;
            left: 0;
            right: 0;
            bottom: 0;
            width: 100%;
        }
        html{
            height: 100vh;
            overflow: hidden;
        }
        body{
            height: 100vh;
            overflow: auto;
        }
    </style>
</head>
<body>
    <div class="content">

    </div>

    <iframe id="inner" src="./inner.html" frameborder="0"></iframe>
</body>
</html>